title: Dosimetric predictors of biochemical control of prostate cancer in patients randomised to external beam radiotherapy with a boost of high dose rate brachytherapy.
abstract: BACKGROUND
  To correlate dose and volume dosimetric parameters (D₉₀ and V₁₀₀) with biochemical control in advanced prostate cancer treated with high-dose rate brachytherapy (HDR-BT).
  
  
  METHODS
  One hundred and eight patients received external beam radiotherapy (EBRT) to 35.75 Gy in 13 fractions followed by HDR-BT of 2 × 8.5 Gy. Kaplan-Meier freedom-from-biochemical relapse (FFbR; nadir+2 μg/L) fits were grouped by the first (Q1), second (Q2) and third (Q3) D₉₀ and V₁₀₀ quartiles. Groups were compared with the log-rank test. Univariate and multivariate Hazard Ratios (HR) for D₉₀ and V₁₀₀ and other co-variates (PSA, androgen deprivation therapy (ADT) were obtained using Cox's proportional hazard model.
  
  
  RESULTS
  FFbR was significantly higher in patients whose D₉₀ and V₁₀₀ were at or above the second and third quartile (log rank p ≤ 0·04). In multivariate analysis D₉₀, V₁₀₀ were significant covariates for risk of relapse.
  
  
  CONCLUSIONS
  Dichotomising the data using 6 levels of response (above and below Q1, Q2 and Q3) showed a progressive and continuous improvement in biochemical control of disease across the entire dose (and volume) range. The data show that a minimum D₉₀ of 108% of the prescribed dose should be the target to achieve.
authors.affiliation: Cancer Centre, Mount Vernon Hospital, Middlesex, UK.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Hoskin
authors.affiliation: Cancer Centre, Mount Vernon Hospital, Middlesex, UK. Electronic address: arc03@btconnect.com.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Rojas
authors.affiliation: Cancer Centre, Mount Vernon Hospital, Middlesex, UK.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Ostler
authors.affiliation: Cancer Centre, Mount Vernon Hospital, Middlesex, UK.
authors.forename: Robert
authors.initials: R
authors.lastname: Hughes
authors.affiliation: Cancer Centre, Mount Vernon Hospital, Middlesex, UK.
authors.forename: Linda
authors.initials: L
authors.lastname: Bryant
authors.affiliation: Cancer Centre, Mount Vernon Hospital, Middlesex, UK.
authors.forename: Gerry J
authors.initials: GJ
authors.lastname: Lowe
mesh_terms: D000368:Aged; D001918:Brachytherapy / Q000379:methods*; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D007610:Kallikreins / Q000378:metabolism; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy; D009367:Neoplasm Staging; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D017430:Prostate-Specific Antigen / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage
chemical_list: C549870:KLK3 protein, human; D007610:Kallikreins; D017430:Prostate-Specific Antigen
keywords: Biochemical control; Dosimetry; High-dose-rate-brachytherapy; Prostate cancer; Randomised trial